In recent years, from the viewpoint of effective utilization of electric energy and the like, an SIC/GaN power semiconductor device equipped with an element using silicon carbide (SIC) and gallium nitride (GaN) has drawn attention (for an example, see Patent Document 1).
Compared to elements that uses Si in the related art, the aforementioned element can not only greatly reduce power loss but also operate at a higher voltage or current and at a high temperature equal to or higher than 200° C. Accordingly, the element is expected to be used in the field to which a Si power semiconductor device in the related art cannot be applied.
Such an element, which is represented by the element (semiconductor element) using SiC/GaN and can operate under harsh conditions, is required to exhibit a higher degree of heat resistance with respect to semiconductor encapsulating materials that are provided to semiconductor devices for protecting the element, compared to the elements in the related art.
In the Si power semiconductor device in the related art, from the viewpoint of adhesiveness, electric stability, and the like, a resin composition that contains a cured material of an epoxy-based resin composition as a main component is used as the semiconductor encapsulating material.
As an index indicating heat resistance of the cured material of a resin composition, a glass transition temperature (Tg) is generally used. This is because the resin composition for encapsulation (cured material) is in the form of rubber in a region having a temperature equal to or higher than Tg, and as a result, the strength or adhesive strength thereof decreases. Therefore, as methods of increasing Tg, techniques such as decreasing an epoxy group equivalent of an epoxy resin contained in a resin composition or decreasing a hydroxyl equivalent of a curing agent (phenol resin curing agent) so as to increase crosslink density, making a rigid structure that links these functional groups (an epoxy group and a hydroxyl group) with each other, and the like are adopted.
In addition to Tg, as an index indicating heat resistance of a resin composition, a weight reduction rate yielded by thermal decomposition is used. The weight of a resin composition is reduced by thermal decomposition caused in a portion in which an epoxy resin and a curing agent are linked to each other with weak bond energy. Accordingly, for a semiconductor encapsulating material having a high functional group density, it is disadvantageous to decrease the weight reduction rate. Therefore, the technique for decreasing the weight reduction rate and the technique for obtaining a high Tg as described above are used for opposed purposes.
Accordingly, in order to enhance heat resistance of a resin composition, it is desirable to design a resin structure, which is formed of an epoxy resin and a curing agent, and a functional group density under optimal conditions so as to obtain a high Tg. Moreover, it is desirable to form a resin composition designed to have a low weight reduction rate.
Moreover, in recent years, in the field of semiconductor and electronic component, improving continuous moldability which significantly influences productivity has become an urgent priority. In this respect, it is desired to improve not only the above characteristics but also the problem in that the semiconductor encapsulating material is incompletely filled in the semiconductor device due to mold contamination caused during continuous molding, clogging of air vent caused by residual burrs, and the like.